Nothing is guaranteed in this year’s NBA Draft, unless your name is Zion Williamson.

Williamson, the freshman sensation from Duke, is widely expected to be the No. 1 selection come June 20.

Michigan freshman forward Ignas Brazdeikis, sophomore guard Jordan Poole and redshirt junior wing Charles Matthews, on the other hand, are far from even being first-round locks. But they do have one thing that bodes well for their draft odds — an invitation to the NBA Combine.

Since the NCAA altered its draft rules in 2016 — moving the withdrawal deadline for underclassmen back nearly a month from late April to 10 days after the combine — there has been a surge in early entrants from the college ranks: 117 in 2016, 137 in 2017, 181 in 2018 and 175 this year.

Throw in international players, the total jumps to 162 in 2016, 182 in 2017, 236 in 2018 and 233 this year.

While the majority of those players did or will withdraw their name from draft consideration, it doesn’t diminish the significance of landing a spot in the annual pre-draft showcase, which features roughly 60-70 participants each year (this year’s official list is expected to be released by the NBA sometime this week).

Simply put, the combine is the best indicator of whom the NBA believes will be selected in its two-round draft. Since 2016, no underclassman who failed to garner an invite to the multi-day event has been taken in the draft.

But over each of the past three years, at least 68.3 percent of combine attendees have ended up being one of the 60 draft picks.

It’s worth noting several lottery picks have declined to participate in the combine in recent years, including 2016 No. 1 pick Ben Simmons, 2018 No. 1 pick Deandre Ayton and eight of the top 11 picks in the 2017 draft.

However, Brazdeikis, Poole and Matthews all plan to attend and fully participate at the combine, according to their respective agents.

The combine, which will run May 14-19 at Quest Multisport Complex in Chicago, will give the three Wolverines an opportunity to make an impression on NBA teams and improve their draft stock. Brazdeikis is projected anywhere from a late first-rounder to a mid-second-round pick, while Poole and Matthews are both predicted to go anywhere from the late second round to undrafted.

Each Wolverine will also have plenty to prove at the event. Brazdeikis (6-foot-7, 215 pounds) is a natural scorer who can finish with both hands around the rim and improved as a 3-point shooter as the season progressed. But there are questions about his passing ability as a perimeter player (31 assists in 37 games) and whether he's quick enough and strong enough to effectively guard threes and fours in the NBA.

Matthews, who tested the draft waters last year but didn’t receive a combine invite, will likely be a three-and-D player at the next level. He has the "D" part down as a versatile defender who can switch and lock down multiple positions. The "three" part still needs to come along and Matthews (6-6, 205) will have to show he can consistently knock down long-range shots better than his numbers have shown (31.8 percent in 2017-18; 29.9 percent in 2018-19).

Poole (6-5, 195) arguably has the most upside of the trio with his enticing offensive skill set and potential to heat up in a hurry. Yet, he has plenty of room to grow as a defender and needs to work on not being so erratic in his offensive execution and decision-making.

While attending the combine gives the three Wolverines a better chance of being drafted, the reality is not all players will. Yet, it still goes a long way to landing in a good spot in the Gatorade League, the NBA’s minor-league system that teams are investing more heavily in.

Last year, nine players who were invited to the combine went undrafted. Two went on to sign guaranteed contracts and play significant minutes with NBA teams — Kenrich Williams with the New Orleans Pelicans and Allonzo Trier with the New York Knicks — while five signed two-way contracts to split time between the NBA and G League, including Bloomfield Hills’ Yante Maten.

In 2017, 17 combine attendees didn't get selected in the draft. Eight ended up signing two-way deals, highlighted by former Wolverine Derrick Walton Jr., who played in 16 games with the Miami Heat during the 2017-18 season.

Matthews and Poole have both made it known they are fully committed to pursuing their professional careers. Brazdeikis has kept the door open to return to Michigan and could possibly take a route similar to former Michigan standout Moritz Wagner, who became a late first-round pick one year after being viewed as a fringe first-rounder. He has until May 29 to make a final decision.

Regardless of where their pro paths take them, Matthews, Poole and, potentially, Brazdeikis will at least have promising odds to be among the 60 players who will hear their name called on draft night next month.

UM’s NBA Draft picks under John Beilein

►Darius Morris, 2011, No. 41 pick: Morris bounced around the league and had stints with five teams in four seasons primarily as a backup point guard. He has since played with two G-League teams and in the Chinese Basketball Association over the last four years.

►Tim Hardaway Jr., 2013, No. 24 pick: Hardaway has had the most successful career to date of Beilein’s draft picks. During his six-year NBA career, Hardaway has averaged double figures in scoring five times and has played at least 65 games four times. He’s also coming off his best season where he averaged career highs in scoring (18.1 points) and starts (63).

►Trey Burke, 2013, No. 9 pick: After a promising start to his pro career, Burke saw his numbers decline and was moved into a backup role in his third and fourth seasons. He began the 2017-18 season in the G League, where he managed to play his way back into the NBA and revive his career.

►Glenn Robinson III, 2014, No. 40 pick: Robinson has spent the majority of his five-year career as a role player with four different teams. His best season came in 2016-17 when he played in a career-high 69 games (27 starts) with the Pacers and averaged a career-best 6.1 points, the only time he’s averaged more than five points per game in a season.

►Mitch McGary, 2014, No. 21 pick: McGary’s time in the NBA didn’t last long. He missed the start of his rookie season with the Thunder with a broken bone in his foot and left the team toward the end of his second year for personal reasons. He was eventually waived after violating the NBA’s anti-drug policy twice and hasn’t played professionally since.

►Nik Stauskas, 2014, No. 8 pick: Stauskas’ high selection hasn’t helped him stick in one spot. He has already been traded three times and has played with five teams in five years. Most of his career has been spent filling a sharpshooter role off the bench.

Caris LeVert(Photo: Matthew Stockman, Getty Images)

►Caris LeVert, 2016, No. 20 pick: Injuries plagued LeVert’s junior and senior seasons at Michigan and provided another roadblock during his breakout 2018-19 campaign. He has improved over each of his three seasons in the NBA and is blossoming into a cornerstone piece for the Nets.

►D.J. Wilson, 2017, No. 17 pick: After a lackluster rookie season that featured multiple G-League stints, Wilson found his footing under Bucks coach Mike Budenholzer as a bench contributor who averaged 5.8 points and 4.6 rebounds in 18.4 minutes per game.

►Moritz Wagner, 2018, No. 25 pick: Wagner missed the first 14 games of his rookie campaign due to injury and his playing time fluctuated throughout most of the season. He received a longer look once the Lakers fell out of the playoff race and wrapped up his first year averaging 4.8 points in 10.4 minutes off the bench.